'\" t
.TH "SD_BUS_START" "3" "" "systemd 256.7" "sd_bus_start"
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.SH "NAME"
sd_bus_start \- Initiate a bus connection to the D\-bus broker daemon
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-bus\&.h>
.fi
.ft
.HP \w'int\ sd_bus_start('u
.BI "int sd_bus_start(sd_bus\ *" "bus" ");"
.SH "DESCRIPTION"
.PP
\fBsd_bus_start()\fR
connects an existing bus connection object to the D\-Bus broker daemon, usually
\fBdbus-daemon\fR(1)
or
\fBdbus-broker\fR(1)\&. The mechanism to use for the connection must be configured before the call to
\fBsd_bus_start()\fR, using one of
\fBsd_bus_set_address\fR(3),
\fBsd_bus_set_fd\fR(3), or
\fBsd_bus_set_exec\fR(3)\&.
\fBsd_bus_start()\fR
will open the connection socket or spawn the executable as needed, and asynchronously start a
\fBorg\&.freedesktop\&.DBus\&.Hello()\fR
call\&. The answer to the Hello call will be processed later from
\fBsd_bus_process\fR(3)\&. If opening of the connection or queuing of the asynchronous call fail, the connection will be closed with
\fBsd_bus_close\fR(3)\&.
.PP
In most cases, it is better to use
\fBsd_bus_default_user\fR(3),
\fBsd_bus_default_system\fR(3)
or related calls instead of the more low\-level
\fBsd_bus_new()\fR
and
\fBsd_bus_start()\fR\&. The higher\-level functions not only allocate a bus object but also start the connection to a well\-known bus in a single function call\&.
.SH "RETURN VALUE"
.PP
On success, this function returns a non\-negative integer\&. On failure, it returns a negative errno\-style error code\&.
.SS "Errors"
.PP
\fB\-EINVAL\fR
.RS 4
The input parameter
\fIbus\fR
is
\fBNULL\fR\&.
.sp
Added in version 246\&.
.RE
.PP
\fB\-ENOPKG\fR
.RS 4
Bus object
\fIbus\fR
could not be resolved\&.
.sp
Added in version 246\&.
.RE
.PP
\fB\-EPERM\fR
.RS 4
The input parameter
\fIbus\fR
is in a wrong state (\fBsd_bus_start()\fR
may only be called once on a newly\-created bus object)\&.
.sp
Added in version 246\&.
.RE
.PP
\fB\-ECHILD\fR
.RS 4
The bus object
\fIbus\fR
was created in a different process\&.
.sp
Added in version 246\&.
.RE
.PP
In addition, other connection\-related errors may be returned\&. See
\fBsd_bus_send\fR(3)\&.
.SH "NOTES"
.PP
Functions described here are available as a shared library, which can be compiled against and linked to with the
\fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
file\&.
.PP
The code described here uses
\fBgetenv\fR(3), which is declared to be not multi\-thread\-safe\&. This means that the code calling the functions described here must not call
\fBsetenv\fR(3)
from a parallel thread\&. It is recommended to only do calls to
\fBsetenv()\fR
from an early phase of the program when no other threads have been started\&.
.SH "HISTORY"
.PP
\fBsd_bus_start()\fR
was added in version 246\&.
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1), \fBsd-bus\fR(3), \fBsd_bus_default\fR(3), \fBsd_bus_call_async\fR(3)
